[graeme]

Those are all true, but:

>For a lot of people, if you get a positive result from a test that a doctor brushes off that's not going to go well.

This is precisely because of the rarity of testing. Suppose the cost of testing dropped 1000x and we could get tests for things each day or each month. We'd start to have systems that put these things on context.

When you have a single isolated result there really isn't that much to go on.